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Confronting the Credibility Gap for Crewed Exploration of Mars

caseyexaustralia.blogspot.com

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Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#51

Post by pilom »

jcoffland wrote: post #37
Animats wrote: post #26

Landing is really hard. Not enough atmosphere for aerobraking, and too far from home to have enough fuel for a powered landing. It's a fuel problem. There's the expensive approach. Send multiple unmanned tanker ships into Mars orbit and have them rendezvous into an orbital supply depot. Send landing tanker ship to rendezvous with them and refuel with enough fuel for a powered landing. Landing ship descends. Repeat to…

How about we harpoon Mars and pull down one end of a space elevator?

The biggest problem with a space elevator on Mars is that the orbit of one of its moons is closer than the minimum height of a space elevator to be stable. Eventually the elevator cable will get hit.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#52

Post by Symmetry »

avmich wrote: post #18

The document linked at the end of the talk currently contains summary regarding the radiation problem on the way to Mars. I've heard of the following approach. The spacecraft generates a magnetic field which spreads around it in flight, having some substantial size (order of kilometers). Relatively small amounts of matter (some gas) are constantly emitted from spacecraft, get ionized and trapped in the magnetic field…

You really want to be piling some dirt on top of your shelters for pressure containment reasons anyways.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#53

Post by Symmetry »

james-watson wrote: post #34

What gets forgotten here, and something that I keep bringing up, is the lack of a Martian magnetosphere. This means long term human settlements have to be artificially shielded. This means living underground, which defeats the point of going to Mars in my opinion. Elon mentioned using a local magnetosphere generator, which is one of those ideas that is theoretically possible but whose practicality seems questionable.…

One of the aspects of Mars that makes living there hard is that Mars is very cold. But that same aspect makes it somewhat easier to establish big magnetic fields on the surface since it means that superconductors will require less cooling. If you're using a superconductor to generate a magnetic field you don't need any continuous input of power.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#54

Post by Jeema101 »

semi-extrinsic wrote: post #41
jcoffland wrote: post #39

Radiation is a huge problem. Both en route and on Mars. A lot of these problems beg the question. Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. Titan for example. Sure it's cold but it has a lot of atmosphere. Presumably landing would be easier. If we could learn to live underwater we could possibly visit Ganymede or Europa.

Radiation, as you mention, is a very big problem which is independent of destination. Human psychology is another, perhaps even bigger problem, also independent of destination. We've had various experiments with prolonged isolation, but none where the subjects know that they're never coming back to Earth. I'd say psychology has a >50% chance of wrecking the first manned missions to other planets/moons, unless we send…

Exactly. Who is going to want to live underground in a freezing wasteland for the rest of their lives after the initial novelty of 'being on Mars' wears off? Nobody even does that here on Earth, so why would they want to do it on Mars?

Floating around in aerostats on the cloud tops of Venus where it's roughly room temperature at 1 atm on the other hand... or living on the Moon where you can at least communicate with Earth in roughly real-time and are only 3 days away...

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#55

Post by lmm »

LeifCarrotson wrote: post #44
lmm wrote: post #40

Earlier quoted context omitted.

The "Red Dragon" missions are planning on the cheap approach, using a flattish (indeed rising in places) trajectory to extend the aerobraking long enough to be effective, combined with supersonic retropropulsion. We've got a lot better at fluid dynamics and lifting-body physics in the last few years, and SpaceX in particular is cleverly developing a lot of experience using the same "EDL technology stack" for their bo…

EDL = Entry/Descent/Landing, for anyone else confused.

Heh, I figured it was ok to use the acronym since it's defined in the article.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#56

Post by LeoDox »

james-watson wrote: post #34

What gets forgotten here, and something that I keep bringing up, is the lack of a Martian magnetosphere. This means long term human settlements have to be artificially shielded. This means living underground, which defeats the point of going to Mars in my opinion. Elon mentioned using a local magnetosphere generator, which is one of those ideas that is theoretically possible but whose practicality seems questionable.…

Mars has an iron core; it's just not molten which prevents it from being ferromagnetic.

I have three questions:

1. Is it merely a question of mass? That is, if Mars were larger would the increased gravity increase pressure at the core and keep it molten?

2. If it IS merely a question of mass, is there any way to add mass to Mars which doesn't disturb its orbit? Because if you could, then you simultaneously solve both the problem of low gravity AND lack of magnetosphere, which together solve the problem of maintaining atmosphere. Basically the whole planet becomes extremely Earth-like

3. If increased mass wouldn't necessarily wreck its orbit, could something be done to "steer" asteroids from the Main Belt into collision courses with Mars?

I really don't know anything about orbital mechanics so maybe there's an obvious flaw in this (aside from the energy required to reroute that many asteroids).

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#57

Post by kwhitefoot »

lmm wrote: post #55
LeifCarrotson wrote: post #44

Earlier quoted context omitted.

EDL = Entry/Descent/Landing, for anyone else confused.

Heh, I figured it was ok to use the acronym since it's defined in the article.

Not everyone reads the articles. I usually skim the comments first to find out if the article might be worth reading; defining the abbreviations definitely helps.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#58

Post by nine_k »

jcoffland wrote: post #39

Radiation is a huge problem. Both en route and on Mars. A lot of these problems beg the question. Is Mars really the best target? Sure it's close but there are moons around Saturn that are interesting as well. Titan for example. Sure it's cold but it has a lot of atmosphere. Presumably landing would be easier. If we could learn to live underwater we could possibly visit Ganymede or Europa.

A floating station (eventually a city?) in the atmosphere of Venus would also be fine. On certain height, the temperature and the pressure are close to Earth's surface, and sun shines brightly enough for plants to generate oxygen. There's plenty of carbon dioxide in the atmosphere to feed the plants.

No roaming over the surface, though.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#59

Post by nine_k »

LeoDox wrote: post #56
james-watson wrote: post #34

What gets forgotten here, and something that I keep bringing up, is the lack of a Martian magnetosphere. This means long term human settlements have to be artificially shielded. This means living underground, which defeats the point of going to Mars in my opinion. Elon mentioned using a local magnetosphere generator, which is one of those ideas that is theoretically possible but whose practicality seems questionable.…

Mars has an iron core; it's just not molten which prevents it from being ferromagnetic. I have three questions: 1. Is it merely a question of mass? That is, if Mars were larger would the increased gravity increase pressure at the core and keep it molten? 2. If it IS merely a question of mass, is there any way to add mass to Mars which doesn't disturb its orbit? Because if you could, then you simultaneously solve both…

The amount of energy required to lower the orbits of enough asteroids (e.g. 20% of Mars total mass) is probably enough to melt a significant portion of Mars. Unfortunately, collisions would mostly heat up the surface, not the core. Even if you could precisely deorbit enough asteroids to hit Mars, the results of the bombardment would probably take a long time to settle.

Planetary-scale engineering is not only hard, it's inevitably slow.

I think cleaning up the atmosphere of Venus by spreading CO2-eating anaerobic air-suspended algae is more realistic, and the results would likely be nicer.

Re: Confronting the Credibility Gap for Crewed Exploration of Mars

#60

Post by chandmer »

Jarwain wrote: post #50
Animats wrote: post #26

Landing is really hard. Not enough atmosphere for aerobraking, and too far from home to have enough fuel for a powered landing. It's a fuel problem. There's the expensive approach. Send multiple unmanned tanker ships into Mars orbit and have them rendezvous into an orbital supply depot. Send landing tanker ship to rendezvous with them and refuel with enough fuel for a powered landing. Landing ship descends. Repeat to…

I feel like a good first step would be setting up an orbital base/space station that orbits mars. It might be be a little easier than habitation On the planet itself, and more risk for the astronauts involved. However, if we set that up using knowledge gleaned from the ISS, I think its a viable path to take.

The attractive thing about landing on dirt is that the raw materials mean that a closed life support system isn't needed. There are relatively accessible supplies. Space stations anywhere, be that LEO, lunar orbit, Mars orbit, deep space, or floating in Venus' atmosphere, lack that option.
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